You will have tweeters housed inside the door mirror covers (just above the wagglers if they are manual mirrors, but it's easy to spot the speaker grille anyway). They're reasonably effective (unless they stop working; my driver's side tweeter stopped but it was immediately obvious) so look for component speakers to go in your round door bins. They have just the one cone and don't have some extra tweeter sitting in front of them (those are called coaxial speakers). So, on this site:
Speakers, 6.5 inch Speakers, 17 cm speakers Pioneer Car Speakers, Alpine Car Speakers, Kenwood , JVC, Focal, Mutant, Car Speakers
www.dynamicsounds.co.uk
look at the component speakers rather than the coaxial ones. You might go down the rabbithole and want to get new tweeters (1") etc etc but some up-specced 17cm/6.5" should impress you enough on the bass front that you're happy to stop right there. It's well worth writing either an email or LiveChat on the website of whatever takes your fancy. These people do this for a living and they should know about what fixing brackets and (quite important) speaker depths will work with a Corsa C. Consider also budgeting for damping and generally getting rid of unwanted vibrations. Assuming that
it's all about the bass, you want to hear the vibration from the cone, not your door metal and long-lost 5p coins dropped down there.
The rear speakers (I don't know, I have a Combo, not a C) are probably co-ax, but who cares about the rear? They can get out and walk if they don't like it. What I do know is that my Focus and Combo Tour has components down at my ankles, tweeters up near my face, and my Modus has just coax down at my ankles. The Modus sounds like
whereas even std setup in the other two is pretty acceptable to me.
